a) Field of the Invention
The present invention relates to water-based protective compositions for coating films. Specifically, the present invention is concerned with water-based protective compositions Which can be applied onto painted or otherwise coated surfaces of motor vehicles, agricultural machines, construction machines and other machines and equipment for their temporary protection.
b) Description of the Prior Art
Commodities such as motor vehicles are prone to fouling, staining, smear or the like at painted or otherwise coated surfaces by wind and rain, moisture, sunlight, air, iron powder, bird droppings, pollutants in the air such as soot, etc. during the periods until they are delivered to end consumers. Their commercial values are hence impaired by these staining To prevent such fouling, various compositions been developed for the protection of coating films in recent years. Developed for such purposes include wax-solvent dispersions (e.g., Japanese Patent Laid-Open No. 28534/1975), removable barrier coats (removable when they become no longer needed; for example, Japanese Patent Publication No. 7303/1979), wax-solid powder-solvent dispersions (hand-wiping is feasible; for example, Japanese Patent Laid-Open No. 149188/1976 or 62978/1980), water-base emulsions (a wax is emulsified and dispersed; for example, Japanese Patent Publication No. 34030/1970), water-base wax-powder dispersions (a wax is emulsified, followed by further dispersion of powder; for example, Japanese Patent Laid-Open No. 177073/1982, U.S. Pat. Nos. 4,442,140 and 4,594,109), acrylic polymer emulsions (an acrylic polymer is emulsified and dispersed; for example, Japanese Patent Publication No. 50517/1980 or Japanese Patent Laid-Open No. 253673/1987), etc.
Among these, wax-solvent dispersions and wax-solid powder-solvent dispersions are widely used these days. These protective compositions however require substantial evaporation of their solvents for the formation of wax barrier coats. Drawbacks of such solvent-type protective compositions, especially, pollution problems, wasting of natural resources, economy and safety are highlighted in recent years. Protective compositions of the wax-solvent dispersion type can show excellent protective performance for coating films. They are however accompanied by the problem that wax barrier coats firmly adhere under the severe environmental conditions in the middle east and tropical regions and they can no longer be removed easily. With a view toward improving this problem, protective compositions of the wax-solid powder-solvent dispersion type have been proposed. These compositions are designed to form wax barrier coats having physical strength low enough to permit removal by hand-wiping. They are however accompanied by the drawbacks that they cannot provide satisfactory protection and their barrier coats are susceptible to separation when touched by hand and are prone to acid rain staining.
On the other hand, water-base wax emulsions do not involve pollution or safety problems because they use no solvent. They are however required to have new properties different from those required for solvent-type wax emulsions, as typified by dryability and water dispersibility. In addition, protective barrier coats which are formed by coating such water-based wax emulsions are required to have the mutually-contradictory properties that they should be strong enough to withstand rain and moisture but they should permit easy removal when they become no longer needed. To the best knowledge of the inventors, compositions of the water-based wax emulsion type capable of meeting these performance and property requirements have not been developed yet.